JPH03211482A - Mls receiving device - Google Patents

Abstract

PURPOSE:To obtain the MLS receiving device which obtains a more effect measurement angle, history information, etc., by reducing demodulation errors by performing AGC over a DPSK signal of each function which arrives next with the level of an arrival beam signal. CONSTITUTION:When a received signal Sa in which beam signals of an azimuth angle and an elevation angle and DPSK signals are arrayed is supplied, a variable gain amplifier A generates and sends out an amplified signal Sb having a value based upon a control signal Sg. The signal Sb is supplied to a DPSK demodulating circuit B and a detecting circuit C to obtain a demodulated signal Sc and detection signals Sd regarding the envelopes. A difference signal generating means D compares one of the signals Sd or their means value with a specific value to generate a difference signal Se and a discriminating means E sends out a discrimination signal Sf for recognizing a DPSK signal generated in the signal Sa after the signal Se is generated from the signal Sc. An amplification control means F sends out a signal Sg for generating the DPSK signal of the signal Sa to the value of the signal Se to the amplifier A. A control means G sends out the signal Sg for generating the signal Sa into the maximum-level signal Sb at need.

Description

[Detailed description of the invention] [Industrial application field] The present invention is a microwave landing system (MLS+M+cro
wave landing system),
The present invention relates to an MLS receiving device mounted on an aircraft or the like to obtain angle measurement and area coverage information.

[Prior Art] In recent years, MLS, which has a wide coverage area and is used to support aircraft's various approach forms and all-weather landings, has a basic configuration of azimuth/elevation (elevation) guidance, distance measurement, Ground equipment such as information transmission (transmission) is deployed close to the runway.
Additionally, the aircraft is equipped with an MLS receiver.

As such an MLS receiving device, the applicant has proposed
An MLS receiver described in Publication No. 3-238482 has been proposed.

This MLS receiver receives the azimuth angle, elevation angle,
Functions such as basic data (hereinafter referred to as Az and E, respectively)
t SBe function) etc. are divided into predetermined time divisions (TDM: Time DivisionMul
tiplex). At this time, first, from the received signal supplied via the variable amplifier,
TRS B in Az, EL function
(Time Reference Scanning
The levels of the TO (outward path) and FRO (return path) pulses of the beam are detected and compared with the reference level to form an AGC signal corresponding to the difference. After this, the beam signal (TO1) related to TDM of the received signal supplied to the variable amplifier is
AGC (closed loop control) is performed in which the FRO pulse is specified and the AGC signal is used to form a constant value. This prevents saturation of the beam signal and accurately measures the azimuth and elevation angles during landing approach.

[Problems to be Solved by the Invention] However, in the above MLS receiver, Az and EL
Dual phase angle modulation wave (DPSK) of function briembunope or basic data etc.
tial Phase 5hift Keying) signal is not subjected to AGC signal processing in the variable gain amplifier, and is supplied to the DPSK demodulation circuit with the maximum gain, where it is demodulated.

Therefore, the desired wave is received with a strong electric field at a position close to the runway, and furthermore, the radio waves of adjacent channels transmitted from ground equipment on other runways, radio waves with strong electric fields such as SSR/PSR, etc. are received by the MLS receiver. It is easy to get mixed in and superimposed on the desired wave. In this case, for example, the variable gain amplifier and DPSK demodulation circuit may cause saturation.
It is conceivable that cross-modulation or the like may occur, leading to demodulation errors in the DPSK demodulation circuit.

The present invention has been made in view of the above problems, and its purpose is to effectively reduce demodulation errors when demodulating a DPSK signal formed in each function, and to obtain more effective angle measurement and coverage information. It is possible to obtain M
An object of the present invention is to provide an LS receiving device.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the MLS receiving device of the present invention, as shown in the claim correspondence diagram of FIG.
A received signal (Sa) in which a beam signal at an elevation angle and a DPSK signal are arranged is supplied to a variable gain amplifier (A), and an amplified signal (Sb) whose value is based on a control signal (Sg) is supplied to a variable gain amplifier (A).
) is sent.

The amplified signal (Sb) is supplied to a DPSK demodulation circuit (B) and a detection circuit (C) to derive a demodulated signal (Sc) and a detection signal (Sd) related to the envelope.

The difference signal generating means (D) to which the detection signal (Sd) is supplied generates a difference signal (Se) by comparing one of the detection signals (Sd) or the average value with a predetermined value.

The identification means (E) sends out an identification signal (Sf) for recognizing the DPSK signal formed in the received signal (Sa) after the generation of the difference signal (Se) from the supplied demodulated signal (Sc).

Next, from the amplification control means (F) to which the difference signal (Se) and the identification signal (Sf) are supplied, the DPSK signal of the received signal (Sa) is formed into a value based on the value of the difference signal (Se). A control signal (Sg) is sent to the variable gain amplifier (A).

Furthermore, in the case where none of the Az and Et functions can be received within a predetermined time, a control signal (S
g) control means (G) for controlling to send out for a predetermined period of time;
Equipped with.

[Operation] In the above configuration, the level of the beam signal in the azimuth angle and the elevation angle, that is, the difference signal (Se) compared with the reference level
DPS formed in time division on the received signal (Sa) by
The level of the K signal is controlled. Furthermore, the received signal (Sa) is kept at the maximum level for a predetermined period of time by the DPSK demodulation circuit (B).
) to respond to the sudden drop in the received signal (Sa), and after this, the level of the DPSK signal is controlled.

[Embodiment] Next, an embodiment of the MLS receiving device according to the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 2 is a block diagram showing the configuration of the embodiment, Fig. 3 is a timing chart showing signal processing waveforms on the time axis in the embodiment, and Figs. 4 and 5 correspond to the operation and control program of the embodiment. It is a flowchart.

In the example shown in FIG. 2, the signal from the antenna is converted and further amplified by a variable gain amplifier 12 which is supplied with a received signal 51 (IF multiplied signal and sends out an amplified signal S2, and a demodulated signal S3). DPSKtI adjustment circuit 14,
Furthermore, it has a detection circuit 16 that derives a detection signal S of the envelope of the amplified signal S2. Furthermore, a Barker code detection circuit 24 that extracts a Barker code signal from the demodulated signal S, and a counter 2 to which the Barker code signal is supplied.
8 and the detection signal S.

a comparator 32.34.36.38 supplied with
It has an RSS flip-flop circuit (R3F/F) 40 to which the comparison signal is supplied. In addition, comparators 32, 34, 36, 38 have +3 dB, +1 dB,
Resistors 42, 44, 46, 48, 49 are connected to apply divided voltages for OdB and -3 dB comparison. Further, a trigger circuit 50 and a register 55.5
6, and a microprocessor (MPU) 52 which includes functional means such as a CPU ROM, RAM, Ilo, and timer in which programs related to overall control are stored, and which derives the angle measurement signal S1°. Subsequently, the D/A converter 54 is supplied with the control signal S derived from the MPU 52, and the analog signal derived therefrom is supplied with the drive signal 5.
12 and supplies the variable gain amplifier 12 with a drive circuit 57 (corresponding to difference signal generation means, identification means, amplification control means, and control means).

Note that the timing generator that generates the clock signal is omitted.

The overall operation of the above configuration will be described below.
AGC (
(closed loop control). Here, TDM is A.
Z, EL function and total time B of DPSK signal
An example will be explained in which the e function is transmitted from the ground device and the A2 function arrives among them (see FIGS. 2 to 5).

Also, the A2 and EL functions have already been received several times, and the gain control value of each function beam is R.
The following explanation assumes that it is stored in AM.

First, in step 101, the RAM is transferred from the MPU 52.
Among the beam gain control values of the Az and EL functions already stored in the control signal S, the control value with the larger gain of the variable gain amplifier 12 is used as a control signal S to instruct transmission.

The control signal S is formed into a drive signal SI2 via the D/A converter 54 and the drive circuit 57, and is then sent to the variable gain amplifier 12.
is supplied to set the amplification gain. variable gain amplifier 1
The reason why AGC is performed using the control value with the larger gain of A2 is to enable reception no matter what function arrives next. or EL function DPSK
This is because the level difference between the modulated preamble and the amplitude modulated beam is only about 6 dB JtL, and the preamble can be detected sufficiently without performing gain control using the level of the DPSK signal. In this way, it waits for the next function to arrive.

In step 102A (auxiliary operation), the received signal S1
is supplied to the variable gain amplifier 12, and the amplified signal S2 derived therefrom is sent to the DPSK demodulation circuit 14 and the detection circuit 1.
6.

Then, the preamble signal of the A2 function in the amplified signal S2 is demodulated by the DPSK demodulation circuit 14, and a demodulated signal S3 is derived. Further, the demodulated signal S3 is supplied to the Barker code detection circuit 24, and the Barker code in the preamble signal serving as a time reference is detected, and the time t shown in FIG. 3(b) is reached. A signal that becomes 1 at the time reference point is supplied to the counter 28, and the counter 28 performs counting using this as a time reference.

In step 103, the function ID signal of the demodulated signal S3 is supplied to the MPU 52. Here, it is identified that the entire arriving signal is the A2 function, and that the guidance signal portion of the A2 function will arrive subsequently, so the gain control value of the Az function is sent as the control signal S, Performs beam gain control.

In step 104A (auxiliary operation), the envelope of the guidance signal of the A2 function (beam<M) is detected, and the detection circuit 16 outputs the T signal shown in FIG. 3(a).
A detected signal S5 containing an O pulse and a FRO pulse is obtained. First, the To pulse is applied to comparators 32, 34, 36 .
38 + (plus) input terminals, where +3 dB, +1 dB, QaE3. It is compared with a set level of -3 dB, and a comparison signal that is the difference is derived. Here, the set level OdB is a reference level that makes the peak values of the To and FRO pulses coincide. In addition, the setting level -
3 dB is a level 3 dB lower than the peak of the pulse. Further, the set levels +1 dB and +3 dB are standards for issuing an alarm when an OCI signal indicating outside the angle measurement range or a reflected wave due to multipath exceeds the peak O dB of the normal beam.

The comparison signals derived from the comparators 32 to 38 in this manner are input by the MPU 52 to the RSF/F 40, which can be read and reset. Further, the comparison signal of the comparator 38 is input to the trigger circuit 50 in order to send out a trigger signal for latching the value of the counter 28 in the registers 55 and 56. Here, the output of the comparator 36 becomes 1 as shown in FIG. 3(C) when the To noise is 13 dB. This output is input to the trigger circuit 50, and the register 55 latches (memorizes) the value of the counter 28 in response to the trigger signal shown in FIG. 3(d).

This is the time t2 of the rise of the To pulse, and at the same time, as shown in FIG. 3 (1), R3F/F40
The output of becomes 1. Next, when the amplitude of the TO pulse increases and reaches a peak, it is compared with a reference level by comparator 36, and the result is latched into RS F/F 40. The amplitude of the TO pulse then decreases to set level -3.
dB, the output of the comparator 38 is inverted as shown in FIG. 3(C), and the trigger circuit 50 is inverted as shown in FIG. 3(e).
A trigger signal shown in is supplied to the register 56 to trigger the counter 2.
The value of 8 is latched into register 56. This is the falling time t of the TO pulse.

In step 105, when the trigger signal is sent to the register 56, the MPU 52 is interrupted;
MPU52 uses R3F/F to read the TO pulse level.
40 output signals f.

g, hS i are stored in the RAM of the MPU 52.

In step 106, the MPU 52 selects R3F/F4
Instructs to reset to 0 and prepares for the arrival of the next FRO pulse. This situation is shown at time t4 in FIGS. 3(5) and 3(i).

In step 107, in order to know the arrival time of the beam, the MPU 52 reads the rise time t2 and fall time t of the TO pulse from the registers 55 and 56, respectively.

In step 108, the MPU 52 at time t3 t
If a is counted and within the specified range, proceed to the next step, and if it is outside the range, proceed to the end.

In step 109, the MPU 52 calculates the arrival time tc of the TO pulse as (tz+t3)/2.

In step 110, if the arrival time tc substantially matches the arrival time (ta.) of the previous TO pulse, it is recognized as a regular TO pulse, and the process proceeds to the next step, where the arrival time 1c is the previous arrival time tT.

If it does not match, it is recognized as a reflected wave due to multipath, and if the level of the reflected wave is higher than that of the regular beam, that is, the R5F/F40 that was stored in the RAM this time.
If the value f or g is 1, an alarm is generated depending on the condition and the process proceeds to the end. Note that the previous value here is the previous value when closed loop control is performed.

In step 111, the arrival time 1c is stored in the RAM and the arrival time ta of the TO pulse is determined. Close it and memorize it.

In steps 112 to 118, the subsequently arriving F
The RO pulses are counted in the same manner as the TO pulses described above, and the arrival time tFlo of the FRO pulse is determined.

In step 119, To
Pulse arrival time t,. and arrival time t of FRO pulse
The MPU 52 reads the FIIO from the RAM and determines the arrival time tT, which is the time interval.

and the arrival time of the FRO pulse tFII[+,
By converting this into an angle, the angle measurement of the A2 function is completed, and the angle measurement signal SIO is sent out.

In step 120, in preparation for the next coming A2 function gain control, the levels of the TO pulse and FRo pulse are read out from the RAM and arithmetic averaged to calculate the next gain control value of the variable gain amplifier 12;
In step 121, the data is stored in the RAM of the MPU 52.

In other words, the output of R3F/F40 when the beam signal arrives (
5) is stored in the RAM so as to lower the gain of the A2 function if it is 1, and to increase it if it is 0. This is set as the gain control value of the next Az function.

In this way, AGC is performed by the MPU 52 so that the beam signal portion always matches the OdB reference level. On the other hand, if the reception rate of the A2 or E or function DPSK signal that can be received within a certain period of time, for example 0.2 seconds, is below the set level, for example 1 or below, the MPU 52
A control signal S for maximizing the gain of the variable gain amplifier 12 is supplied from the drive circuit 57 to the D/A converter 54, and a drive signal S is supplied from the drive circuit 57 to the variable gain amplifier 12. The maximum gain control time is, for example, 3 seconds, and the AGC of the DPSK signal is restarted based on the level values of the To and FRO pulses obtained during this time. This enables effective control even when the level of the AZ s EL function drops rapidly.

Although the above embodiment has been described as an example in which the A2 function in TDM arrives, it can also be applied to other TDM functions, such as AGC of the DPSK signal portion of the preamble of the EL SBc s reverse direction, flare height and low functions. It is possible. Furthermore, in the above embodiment, TO1
Although the arithmetic mean value of the FRO pulse is used, the AGC of the DPSK signal portion may be performed using one of the values having a smaller level. Further, although the explanation has been made using the TO1FRO pulse level b<x21 level, which is larger than the level b<x21, it goes without saying that even in the opposite case, that is, when the TO1FRO level is smaller than the reference level, AGC is possible using this level difference.

Further, in the above embodiment, the counter 28 and the comparator 3
2 to 38, R3F/F40, trigger circuit 50 and MP0
52, etc., to perform the signal processing, but the invention is not limited thereto. For example, the present invention also includes storing a digitized signal obtained by quantizing the detection signal S5 in a RAM or the like, and further using a computer or the like to perform the same control/arithmetic processing as described above to obtain the same effect.

[Effects of the Invention] As is clear from the above description, the MLS receiving device of the present invention has the following effects and advantages. That is, by performing AGC on the next arriving DPSK signal of each function using the level of the incoming beam signal,
Saturation, cross-modulation, etc. in signal processing are effectively reduced,
This has the effect that demodulation errors when demodulating the DPSK signal formed in each function are reduced, making it possible to obtain more effective angle measurements, coverage information, and the like.

[Brief explanation of drawings]

FIG. 1 is a claim correspondence diagram relating to the MLS receiving device of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of the MLS receiving device according to the present invention, and FIG. 3 is a time diagram in the embodiment of FIG. 1. Timing charts showing signal processing waveforms on the axis, and FIGS. 4 and 5 are flowcharts corresponding to the operation and control program of the embodiment shown in FIG. 1. 2... Variable gain amplifier 4... DPSK demodulation circuit 6... Detection circuit 4... Barker code detection circuit 8... Counter 2.34.36.38... Comparator 0... RS
Flip-flop circuit 0...Trigger circuit 2...MPU 4...D/A converter 55,56...Register 57...Drive circuit Sl...Received signal S2...Amplified signal S3...・Demodulation signal S, ... detection signal S, ... control signal Sho ... angle measurement signal S1□ ... drive signal FIG, 1

Claims (3)

[Claims] (1) A variable gain amplifier that forms a received signal in which at least a beam signal related to an azimuth angle and an elevation angle and a DPSK signal are arranged into an amplified signal based on a supplied control signal and sends it out, and the amplified signal is supplied. DPSK to derive the demodulated signal
a demodulation circuit; a detection circuit to which the amplified signal is supplied and which derives an envelope detection signal from each of the azimuth and elevation beam signals; and one of the azimuth and elevation envelope detection signals or an average value. a difference signal generating means for generating a difference signal by comparing the difference signal with a predetermined value; and a means for generating a difference signal, which is supplied with the demodulated signal and recognizes a DPSK signal formed in the received signal after creating the difference signal, and sends out an identification signal. identification means for determining the DP of the received signal by being supplied with the difference signal and the identification signal;
An MLS receiver comprising: amplification control means for sending a control signal for forming an SK signal to a value based on the value of the difference signal to a variable gain amplifier. (2) The apparatus according to claim 1, further comprising control means for controlling the control signal for forming the received signal into an amplified signal of the maximum level to be transmitted for a predetermined period of time when the reception rate of the DPSK signal is below a set level. MLS receiving device. (3) The apparatus according to claim 1, wherein the difference signal generation means and the amplification control means include at least a comparator, a Barker code signal detection circuit, a counter, a register, a microprocessor, and a D/A converter. MLS receiving device.